Compositions and methods for delayed crosslinking in hydraulic fracturing fluids

ABSTRACT

Disclosed herein are compositions and methods for delaying crosslinking of aqueous crosslinkable polymers such as polysaccharides in injectable compositions for hydraulic fracturing and related applications. The compositions and methods provide delayed crosslinking at high temperatures and pressures, such as those encountered by hydraulic fracturing compositions injected into subterranean environments. Compositions include injectable solutions comprising a competing agent that is a reaction product of a dialdehyde having 2 to 4 carbon atoms with a non-polymeric cis-hydroxyl compound. Provided are methods of making and using delayed-crosslinking compositions comprising crosslinker compositions containing zirconium complexes and the competing agents.

TECHNICAL FIELD

The present invention relates to compositions and methods for delayingcrosslinking of polymers effected by a variety of complexes in water.

BACKGROUND

Hydraulic fracturing is a well-stimulation technique in whichsubterranean rock is fractured by a hydraulically pressurized fracturingfluid typically made by combining water or an aqueous liquid, ahydraulic fracturing proppant (conventionally sand or aluminum oxide),and additive chemicals that modify subterranean flow, subterraneaninterfacial tension, and/or provide other effects. A hydraulic fractureis formed by pumping the fracturing fluid into a wellbore at a ratesufficient to increase pressure at the target depth to exceed that ofthe fracture gradient (pressure gradient) of the rock. When thehydraulic pressure is removed from the well, the hydraulic fracturingproppants lodge within the cracks to hold the fractures open.Hydrocarbon compounds such as natural gas and petroleum are recoveredvia the cracks in the hydrocarbon-containing deep-rock formations.Hydraulic fracturing techniques can be used to form a new well and canalso be used to extend the life of an existing conventional oil well.

In recent years the hydraulic fracturing industry has turned torecycling the water that flows back from the subterranean formationsafter release of hydraulic pressure thereto. Such water is referred toas “produced water.” Produced water is often characterized as havinghigh total dissolved solids, such as at least about 1 wt % totaldissolved solids and as much as about 35 wt % total dissolved solids, inaddition to any residual fracturing fluid chemicals flowing back fromthe injection thereof. Stated differently, the dissolved solids inproduced water are derived principally from the subterranean reservoiritself. In most cases, a substantial portion of the dissolved solids areionic (one or more salts). Rather than treat the produced water toremove dissolved solids, it is economically more practical to simply usethe produced water with no further treatment prior to use as afracturing liquid.

Chemical additives including surfactants and polymers have been added tofracturing fluids in hydraulic fracturing processes to increase recoveryof hydrocarbon compounds from subterranean hydrocarbon-containingformations by controlling interfacial energy of the fluid with thesubterranean features such as various rock types, to control frictioncaused by the fracturing fluid as it flows within the subterraneanformation and through narrow tubulars, to control viscosity of thefracturing fluid, or two or more thereof.

In order to carry the proppant particles used to keep the cracks in thesubsurface formation open once they are fractured, the fracturing fluidneeds to be able to carry these particles all the way down and intothese cracks. One way of doing this is to increase the viscosity of thefracturing fluid. Crosslinking provides one means by which the viscosityof fracturing fluids can be increased.

A problem encountered during hydraulic fracturing is the loss of fluidinjectivity in areas of relatively low permeability due to preferentialflow of the fracturing fluid into higher permeability areas, sometimesknown as “channeling”. Oil bearing strata are usually heterogeneous,some parts of them being more permeable than others. As a consequence,channeling can occur so that the driving fluid flows preferentiallythrough permeable zone depleted of oil (so-called “thief zones”) ratherthan through those parts of the strata that contain sufficient oil tomake oil-recovery operations profitable. Difficulties in oil recoverydue to high permeability of zones may be corrected by injecting anaqueous solution of an organic polymer and a crosslinking agent intocertain subterranean formations where the polymer will be crosslinked toproduce a gel, thus reducing the permeability of such subterraneanformations to driving fluid (gas, water, etc.).

Crosslinked fluids or gels are now being used in wells under a varietyof temperature and pH conditions. Polysaccharide or partially hydrolyzedpolyacrylamide-based fluids crosslinked with certain aluminum, titanium,zirconium, and boron-based compounds are used in enhanced oil recoveryoperations. Such fracturing fluids can encounter a variety of conditionsof high temperature and pressure in subterranean formations.

A disadvantage with many of the known crosslinkers is that they cancause an immediate and excessive increase in viscosity of the fracturingfluids to which they are added. Excessive viscosity increase before thefracturing fluid has sufficiently penetrated the subterranean formationincreases strain on pumping equipment and/or requires greater energyconsumption to pump the fracturing fluids into the subterraneanformations. Excessive fracturing fluid viscosity can also increase shearin the pumping equipment, causing degradation of components within thefracturing fluid and leading to degradation in fracturing fluidperformance.

A further issue encountered is that produced waters can containdissolved reactive species such as boric acid and/or borate oxyanions,which can function as crosslinkers for polysaccharides and causepremature crosslinking of hydraulic fracturing fluids comprisingpolysaccharides and produced waters.

It would be advantageous to provide hydraulic fracturing compositionsand methods for use in a variety of different subterranean conditions,which would allow for penetration of low-permeability zones in additionto or instead of thief zones by proppant bearing fluid. It would befurther advantageous if such fluids could be used at the hightemperatures and pressures found in deep subterranean locations.

SUMMARY

In embodiments, there is provided an injectable solution comprising acrosslinkable polymer, a competing agent comprising the reaction productof a dialdehyde having 2 to 4 carbon atoms with a non-polymericcis-hydroxyl compound, a crosslinker composition, and at least one watersource. In embodiments, the crosslinkable polymer is a polysaccharide.In some embodiments, the crosslinkable polymer is carboxymethylhydroxypropyl guar. In embodiments, the competing agent is the reactionproduct of glyoxal and sorbitol. In embodiments, the crosslinkercomposition is the reaction product of zirconium (IV) tetra(n-propoxide)and triethanolamine in n-propanol. In some such embodiments, thecrosslinker composition is the reaction product of zirconium (IV)tetra(n-propoxide) and triethanolamine in a 1:9 molar ratio. Inembodiments, the water source comprises, consists of, or consistsessentially of produced water.

In embodiments, there is provided a method of making adelayed-crosslinking composition, the method comprising combining adialdehyde having 2 to 4 carbon atoms with a non-polymeric cis-hydroxylcompound in an aqueous solution to form a competing agent solutioncomprising a competing agent, adjusting the pH of the competing agentsolution to maintain a pH of about 6.0 to about 6.5, combining azirconium (IV) compound and an alkanolamine in one or more solvents toform a crosslinker composition comprising a zirconium complex,maintaining the crosslinker composition at a temperature of from about35° C. to about 40° C. for 90 to 150 minutes, and combining thecompeting agent solution and the crosslinker composition to form adelayed-crosslinking composition. In embodiments, the dialdehydecomprises, consists of, or consists essentially of glyoxal. Inembodiments, the cis-hydroxyl compound is sorbitol. In embodiments, thezirconium (IV) compound comprises, consists of, or consists essentiallyof zirconium (IV) tetra(n-propoxide). In embodiments, the alkanolaminecomprises, consists of, or consists essentially of triethanolamine. Inembodiments, the one or more solvents comprises, consists of, orconsists essentially of n-propanol.

In embodiments, the method further comprises combining thedelayed-crosslinking composition with a water source and a crosslinkablepolymer to form an injectable solution, injecting the injectablesolution into a subterranean reservoir, and recovering a hydrocarbonfrom the reservoir. In embodiments, the water source comprises, consistsof, or consists essentially of produced water.

Additional advantages and novel features of the invention will be setforth in part in the description that follows, and in part will becomeapparent to those skilled in the art upon examination of the following,or may be learned through routine experimentation upon practice of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plot of viscosity as a function of time for threeinjectable solutions with the same competing agent solutions.

FIG. 2 shows a plot of viscosity as a function of time for threeinjectable solutions having three different competing agent solutions.

DETAILED DESCRIPTION

Although the present disclosure provides references to preferredembodiments, persons skilled in the art will recognize that changes maybe made in form and detail without departing from the spirit and scopeof the invention. Reference to various embodiments does not limit thescope of the claims attached hereto. Additionally, any examples setforth in this specification are not intended to be limiting and merelyset forth some of the many possible embodiments for the appended claims.

Definitions

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art. In case of conflict, the present document, includingdefinitions, will control.

As used herein, the term “produced water” means connate (native waterwithin a reservoir prior to flowback) or flowback water (water thatflows from a subterranean reservoir after one or more hydraulicfracturing or other well formation operations). In some embodiments, theproduced water contains about 10 ppm to 500 ppm dissolved reactive boronspecies. In some embodiments, the connate or flowback further contains500 ppm total dissolved solids to 1000 ppm total dissolved solids, insome embodiments, 1000 ppm to 10,000 ppm, in some embodiments10,000-50,000 ppm, or in some embodiments 50,000 ppm to 100,000 ppm, inembodiments 100,000-500,000 ppm total dissolved solids.

As used herein, the term “reactive species” means a compound capable ofparticipating in crosslinking reactions with compounds having one ormore cis-hydroxyl moieties, unfunctionalized polysaccharides such asguar gum, and/or functionalized polysaccharides such as carboxymethylhydroxypropyl guar.

As used herein, the term “reactive boron species” means boric acid,tetrahydroxyborate, or another boron-containing compound capable offorming orthoborate (B(OH)₄ ⁻) or another boron-containing oxyanionstructure at pH of greater than about 6.5 and/or capable ofparticipating in crosslinking reactions with compounds having one ormore cis-hydroxyl moieties, unfunctionalized polysaccharides such asguar gum, and/or functionalized polysaccharides such as carboxymethylhydroxypropyl guar.

As used herein, the term “source of dissolved reactive boron species”means a source of a compound that is a reactive boron species, or iscapable of forming one by chemical transformation or slow dissolution.

As used herein, “complex” means inter alia not only a moiety comprisinga metal atom or a metal ion bonded to and/or associated with one or moreligands but also a metalloid atom or ion bonded to and associated withone or more ligands. Ligands can be monodentate, bidentate, and/orpolydentate. In this context, ligands can be atoms, ions, molecules,other chemical structures, or combinations thereof. In this context,non-limiting examples of metalloids include boron, silicon, germanium,and antimony. Herein, the term “complex” includes any molecule or ionwith a central atom, atoms, ion, or ions having ligands bonded theretoor associated therewith, the complex being capable of crosslinking thecrosslinkable polymer. Thus “complex” includes borate oxyanions inaddition to more conventional metal complexes with various ligands, andthe term includes metal and metalloid oxides, hydroxides, and hydratedoxides with the proviso that they are capable of crosslinking thepolymer having cis-functionality.

As used herein, “crosslinker composition” means a composition comprisinga crosslinker, wherein the crosslinker is capable of crosslinking acrosslinkable polymer.

As used herein, the term “polymer solution” denotes a polymer eitherdispersed or dissolved in one or more solvents.

As used herein, the term “cis-hydroxyl” denotes a compound having atleast one pair of hydroxyl groups situated in a 1,2 configuration,further wherein the hydroxyls are configured to allow the coordinationthereof with a boron oxyanion or a metal complex center.

As used herein, the terms “comprise(s),” “include(s),” “having,” “has,”“can,” “contain(s),” and variants thereof are intended to be open-endedtransitional phrases, terms, or words that do not preclude thepossibility of additional acts or structures. The singular forms “a,”“and” and “the” include plural references unless the context clearlydictates otherwise. The present disclosure also contemplates otherembodiments “comprising,” “consisting of” and “consisting essentiallyof,” the embodiments or elements presented herein, whether explicitlyset forth or not.

As used herein, the term “optional” or “optionally” means that thesubsequently described event or circumstance may but need not occur, andthat the description includes instances where the event or circumstanceoccurs and instances in which it does not.

As used herein, the term “about” modifying, for example, the quantity ofan ingredient in a composition, concentration, volume, processtemperature, process time, yield, flow rate, pressure, and like values,and ranges thereof, employed in describing the embodiments of thedisclosure, refers to variation in the numerical quantity that canoccur, for example, through typical measuring and handling proceduresused for making compounds, compositions, concentrates or useformulations; through inadvertent error in these procedures; throughdifferences in the manufacture, source, or purity of starting materialsor ingredients used to carry out the methods, and like proximateconsiderations. The term “about” also encompasses amounts that differdue to aging of a formulation with a particular initial concentration ormixture, and amounts that differ due to mixing or processing aformulation with a particular initial concentration or mixture. Wheremodified by the term “about” the claims appended hereto includeequivalents to these quantities. Further, where “about” is employed todescribe a range of values, for example “about 1 to 5” or “about 1 toabout 5”, the recitation means “1 to 5” and “about 1 to about 5” and “1to about 5” and “about 1 to 5” unless specifically limited by context.

As used herein, the term “consisting essentially of” means that themethods and compositions may include additional steps, components,ingredients or the like, but only if the additional steps, componentsand/or ingredients do not materially alter the basic and novelcharacteristics of the claimed methods and compositions.

Discussion

Preferred methods and materials are described below, although methodsand materials similar or equivalent to those described herein can beused in practice or testing of the present invention. All publications,patent applications, patents and other references mentioned herein areincorporated by reference in their entirety. The materials, methods, andexamples disclosed herein are illustrative only and not intended to belimiting.

First Embodiments

In first embodiments of the invention, there is provided an injectablesolution comprising a crosslinkable polymer, a competing agentcomprising the reaction product of a dialdehyde having 2 to 4 carbonatoms with a non-polymeric cis-hydroxyl compound, and at least one watersource. In embodiments, the at least one water source comprises,consists of, or consists essentially of a produced water. In some suchfirst embodiments, the injectable solution further comprises acrosslinker composition comprising, consisting of, or consistingessentially of one or more crosslinkers.

In embodiments, the one or more crosslinkers comprises, consists of, orconsists essentially of a complex. In some embodiments, the at least onewater source comprises one or more reactive species that acts as acrosslinker for the crosslinkable polymer. In other embodiments, the atleast one water source does not comprise one or more reactive speciesthat acts as a crosslinker for the crosslinkable polymer.

In some of the first embodiments, the injectable solution is made bycombining at least one water source, a crosslinkable polymer, thecompeting agent, and the crosslinker composition comprising one or morecrosslinkers. The at least one water source is selected from producedwater, tap water, ground water, surface water, seawater, wastewater,deionized water, distilled water, or any combination thereof. Inembodiments, the at least one water source comprises, consists of, orconsists essentially of produced water. The terms produced water, tapwater, ground water, surface water, seawater, wastewater, deionizedwater, and distilled water herein are construed to include such watersources having undergone further processing such as adulteration; orpurification steps such as, but not limited to, filtration, activatedcarbon treatment, lime softening, sedimentation, and the like.

In some of the first embodiments, the injectable solution of the firstembodiments is made by combining the at least one water source; thecrosslinkable polymer; a competing agent solution comprising, consistingof, or consisting essentially of the competing agent and one or morecompeting agent solvents, and the crosslinker composition comprising oneor more crosslinkers. In some such embodiments, the one or morecompeting agent solvents comprises, consists of, or consists essentiallyof a water source selected from produced water, tap water, ground water,surface water, seawater, wastewater, deionized water, distilled water,or any combination thereof.

In embodiments, the injectable solution of the first embodiments is madeby combining an aqueous solution of the crosslinkable polymer, thecompeting agent solution, and the crosslinker composition. In some suchembodiments, the aqueous solution of the crosslinkable polymercomprises, consists of, or consists essentially of the crosslinkablepolymer and a produced water, tap water, ground water, surface water,seawater, wastewater, deionized water, distilled water, or anycombination thereof.

In embodiments, the injectable solution of the first embodiments is madeby combining the at least one water source, the aqueous solution of thecrosslinkable polymer, the competing agent solution, and the crosslinkercomposition.

In embodiments, the injectable solution of the first embodiments is madeby combining the at least one water source, the crosslinkable polymer,and a delayed-crosslinking composition, wherein the delayed-crosslinkingcomposition comprises, consists of, or consists essentially of thecompeting agent solution and the crosslinker composition. Inembodiments, the crosslinker composition comprises a zirconium (IV)complex.

In embodiments, the injectable solution of the first embodiments is madeby combining the aqueous solution of the crosslinkable polymer and thedelayed-crosslinking composition.

In embodiments, the injectable solution of the first embodiments is madeby combining the at least one water source, the aqueous solution of thecrosslinkable polymer, and the delayed-crosslinking composition.

The crosslinker composition of the first embodiments comprises, consistsof, or consists essentially of one or more crosslinkers. The one or morecrosslinkers are capable of crosslinking the crosslinkable polymer. Inembodiments, one or more of the one or more crosslinkers is a complex.In embodiments, the one or more crosslinkers comprises an aluminum,antimony, boron, chromium, copper, iron, lead, manganese, niobium,titanium, zinc, or zirconium complex, wherein the complex has a centralatom or ion selected from aluminum, antimony, boron, chromium, copper,iron, lead, manganese, niobium, titanium, zinc, or zirconiumrespectively, and has a coordination number of between two and six. Inembodiments, the complex is a reactive boron species. In embodiments,the crosslinker composition comprises, consists of, or consistsessentially of a complex of a metal and one or more ligands selectedfrom alkanolamine, lactate, citrate, maleate, citraconate, tartrate,bitartrate, primary organic amine, secondary organic amine, tertiaryorganic amine, or acac (acetylacetonate). In some such embodiments, thealkanolamine comprises, consists of, or consists essentially oftriethanolamine. In embodiments, the crosslinker composition comprises azirconium complex. In embodiments, the zirconium complex comprises,consists of, or consists essentially of a zirconium (IV) complex that isthe reaction product of tetra(n-propoxy) zirconium with an alkanolamine.In some such embodiments, the zirconium complex is a zirconium (IV)complex that is the reaction product of tetra(n-propoxy) zirconium withtriethanolamine.

In embodiments, the molar ratio of the zirconium complex to thecompeting agent in the crosslinker composition is about 5:1 to 1:20, inembodiments 5:1 to 1:10, in embodiments 5:1 to 1:5, in embodiments 5:1to 1:1, in embodiments, 5:1 to 2:1, in embodiments 5:1 to 3:1, inembodiments about 4:1, in embodiments 3.9:1. In some such embodiments,the molar ratio is the molar ratio of sorbitol equivalent to zirconiumin the injectable solution. The sorbitol equivalent is the amount of thereaction product of sorbitol and the dialdehyde plus the amount of anyunreacted sorbitol.

In embodiments, the crosslinker composition is a product obtained bycombining a zirconium (IV) alkoxide and an alkanolamine. In embodiments,the crosslinker composition is a product obtained by combining azirconium tetraalkoxide and an alkanolamine. In embodiments, thealkanolamine comprises, consists of, or consists essentially oftriethanolamine. In embodiments, the crosslinker is the product ofcombining a zirconium tetraalkoxide solution in a first alcoholicsolvent with an alkanolamine. In embodiments, the alkanolamine is notdissolved or dispersed in a solvent. In embodiments, the alkanolamine isdissolved and/or dispersed in a second alcoholic solvent. Inembodiments, the first and second alcoholic solvents are the same. Inembodiments, the first and second alcoholic solvents are different. Inembodiments, each of the first and second alcoholic solvents comprises,consists of, or consists essentially of a C1 to C7 alcohol. Inembodiments, the crosslinker composition is the product of combiningtriethanolamine with a zirconium tetraalkoxide solution in a C1 to C7alcohol. In embodiments, the crosslinker composition is the product ofcombining triethanolamine with a zirconium tetra(n-propoxide) solutionin n-propanol. In embodiments, the crosslinker composition is theproduct of combining triethanolamine and a zirconium tetra(isopropoxide)solution in a first alcoholic solvent comprising, consisting of, orconsisting essentially of isopropanol. In embodiments, the crosslinkercomposition is the product of combining triethanolamine and a zirconiumtetra(n-butoxide) solution in a first alcoholic solvent comprising,consisting of, or consisting essentially of n-butanol. In embodiments,the crosslinker composition is the product of combining triethanolamineand a zirconium tetra(t-butoxide) solution in a first alcoholic solventcomprising, consisting of, or consisting essentially of t-butanol. Inembodiments, the crosslinker composition is the product of combiningtriethanolamine and a zirconium tetra(i-butoxide) solution in a firstalcoholic solvent comprising, consisting of, or consisting essentiallyof i-butanol. In embodiments, the crosslinker composition is the productof combining triethanolamine and a zirconium tetraethoxide solution in afirst alcoholic solvent comprising, consisting of, or consistingessentially of ethanol. In embodiments, the molar ratio of the zirconiumtetraalkoxide to alkanolamine is from about 1:5 to about 1:11, inembodiments about 1:6 to 1:11, in embodiments about 1:7 to about 1:10,in embodiments about 1:8 to 1:10, in embodiments about 1:9. In some suchembodiments, the alkanolamine comprises, consists of, or consistsessentially of triethanolamine.

Applicants have found that crosslinker compositions that are the productof combining zirconium tetra(alkoxide) and triethanolamine in a molarratio of 1:8 to 1:10 respectively are especially useful for combinationwith a competing agent comprising the reaction product of a dialdehydehaving 2 to 4 carbon atoms with a non-polymeric cis-hydroxyl compound toprovide a delayed-crosslinking composition for addition to apolysaccharide such as carboxymethyl hydroxypropyl guar to provideinjectable solutions for high downhole temperature applications such asup to 200° C. In such applications, Applicants have found that thecompeting agent that is the product of the reaction of glyoxal andsorbitol is useful.

Second Embodiments

In the second embodiments of the invention, there is provided aninjectable solution comprising a crosslinkable polymer, a competingagent comprising the reaction product of a dialdehyde having 2 to 4carbon atoms with a non-polymeric cis-hydroxyl compound, and at leastone water source comprising one or more reactive species. Inembodiments, the at least one water source comprises, consists of, orconsists essentially of produced water. In the second embodiments of theinvention, no additional crosslinker is added to the injectablesolution, but the crosslinker is supplied by the water source as one ormore reactive species. The crosslinker consists of or consistsessentially of one or more dissolved reactive species present as anative species in the at least one water source. In embodiments, the atleast one water source comprises, consists of, or consists essentiallyof produced water comprising the one or more dissolved reactive speciespresent as a native species in the produced water. In embodiments, thenative species in the produced water comprises, consists of, or consistsessentially of a reactive boron species. In embodiments, the injectablesolution is made by combining the at least one water source comprisingone or more reactive species, the crosslinkable polymer, and thecompeting agent. In embodiments, the at least one water source isselected from produced water, tap water, ground water, surface water,seawater, wastewater, deionized water, distilled water, or anycombination thereof, with the proviso that the at least one water sourcecomprises one or more reactive species. The terms produced water, tapwater, ground water, surface water, seawater, wastewater, deionizedwater, and distilled water herein are construed to include such watersources having undergone further processing such as adulteration; orpurification steps such as, but not limited to, filtration, activatedcarbon treatment, lime softening, sedimentation, and the like.

In some second embodiments, the injectable solution of the secondembodiments is made by combining the at least one water source, thecrosslinkable polymer, and a competing agent solution comprising,consisting of, or consisting essentially of the competing agent and oneor more competing agent solvents. In embodiments, the one or morecompeting agent solvents comprises, consists of, or consists essentiallyof a water source selected from produced water, tap water, ground water,surface water, seawater, wastewater, deionized water, distilled water,or any combination thereof.

In embodiments, the injectable solution of the second embodiments ismade by combining the at least one water source, an aqueous solution ofthe crosslinkable polymer, and the competing agent solution.

In some second embodiments of the invention, the produced watercomprises about 10 ppm to 500 ppm boron as dissolved reactive boronspecies. In such embodiments, the dissolved reactive boron species is atleast one of one or more crosslinkers that crosslinks the crosslinkablepolymer.

In embodiments, the crosslinkable polymer of the second embodiments is acis-hydroxyl polymer. In some such embodiments, the crosslinkablepolymer is guar.

Third Embodiments

In third embodiments, there is provided a method comprising combining adialdehyde having 2 to 4 carbon atoms with a non-polymeric cis-hydroxylcompound in an aqueous solution to form a competing agent solutioncomprising a competing agent; adjusting the pH of the competing agentsolution to maintain a pH of about 6.0 to about 6.5; combining azirconium (IV) compound and an alkanolamine in one or more solvents toform a crosslinker composition comprising a zirconium complex; andmaintaining the crosslinker composition at a temperature of betweenabout 35° C. and 40° C. for 90 to 150 minutes. In embodiments, thecrosslinker composition is allowed to cool to ambient temperature.

In embodiments, the method further comprises combining the crosslinkercomposition and the competing agent solution to form adelayed-crosslinking composition.

In embodiments, the combining the zirconium (IV) compound and thealkanolamine in one or more solvents comprises, consists of, or consistsessentially of combining the alkanolamine with a solution of thezirconium (IV) compound in the one or more solvents. In embodiments, thecombining in one or more solvents comprises, consists of, or consistsessentially of combining the zirconium (IV) complex in a first solventor first solvent mixture with the alkanolamine in a second solvent orsolvent mixture, wherein the one or more solvents consists of orconsists essentially of the first solvent or first solvent mixture andthe second solvent or solvent mixture. In embodiments, the one or moresolvents comprises, consists of, or consists essentially of one or moreC1 to C7 alcohols. In embodiments, the one or more solvents comprises,consists of, or consists essentially of n-propanol. In embodiments, thecombining is carried out at a temperature between 15° C. and 70° C., inembodiments between 15° C. and 60° C., in embodiments between 15° C. and50° C., in embodiments between about 15° C. and about 46° C.; in suchembodiments, the combining results in an exotherm that warms up thecrosslinker composition. The temperature of the crosslinker compositionis kept within the aforementioned prescribed limits by cooling thezirconium compound, the alkanolamine, the one or more solvents, thecrosslinker composition, or any combination thereof. It can also beachieved by controlling the rate of the combining—the slower the rate,the lower the maximum temperature attained and the lower the temperaturenot exceeded. In embodiments, the combining in one or more solventscomprises, consists of, or consists essentially of combining thealkanolamine with the zirconium (IV) compound in the one or moresolvents to form the crosslinker composition. In such embodiments, anexotherm results, causing the resulting mixture to warm up. Inembodiments, the combining comprises, consists of, or consistsessentially of adding the alkanolamine to a solution of the zirconium(IV) compound in the one or more solvents. In some such embodiments, theadding is effected at such a rate as to avoid the temperature of thecrosslinker composition exceeding 70° C., in embodiments exceeding 60°C., in embodiments exceeding 50° C., in embodiments exceeding about 46°C. In embodiments the alkanolamine comprises, consists of, or consistsessentially of triethanolamine. In embodiments, the zirconium (IV)compound is a zirconium tetraalkoxide. In embodiments, the zirconium(IV) compound is zirconium tetra(n-propoxide). In some such embodiments,the one or more solvents comprises, consists of, or consists essentiallyof n-propanol. In embodiments, the molar ratio of the zirconium (IV)compound to alkanolamine is between about 1:5 and about 1:11, inembodiments about 1:6 to 1:11, in embodiments about 1:7 to about 1:10,in embodiments about 1:8 to 1:10, in embodiments about 1:9. In some suchembodiments, the alkanolamine comprises, consists of, or consistsessentially of triethanolamine. In embodiments, after the combining ofthe zirconium (IV) compound and the alkanolamine in the one or moresolvents and after an exotherm resulting from the combining, the methodfurther comprises maintaining the crosslinker composition at atemperature of from about 35° C. to about 40° C. for about 60 minutes toabout 200 minutes, in embodiments about 90 to about 150 minutes, inembodiments about 120 minutes.

In embodiments, the non-polymeric cis-hydroxyl compound comprises,consists of, or consists essentially of a sugar alcohol having 3 to 7carbon atoms selected from erythritol, threitol, pentaerythritol,arabitol, xylitol, ribitol, mannitol, sorbitol, galactitol, fucitol,iditol, inositol, volemitol, glycerol, or a combination thereof. Inembodiments, the non-polymeric cis-hydroxyl compound is sorbitol. Inembodiments the dialdehyde is selected from glyoxal, maleic dialdehyde,fumaric dialdehyde, glutaric dialdehyde, and the reaction product ofglucose with NaIO₄. In embodiments, the dialdehyde is glyoxal. Inembodiments, the competing agent is the reaction product of thedialdehyde and the non-polymeric cis-hydroxyl compound in a 3:1 to 1:3molar ratio, in embodiments 2:1 to 1:2 molar ratio, in embodiments abouta 1:1 molar ratio. The dialdehyde and the cis-hydroxyl compound aresuitably combined in water in about a 3:1 to 1:3 molar ratio, or inabout a 2:1 to 1:2 molar ratio, or in about a 1:1 molar ratio to form acombination in water. In embodiments, the combination in water is leftmixing for 1-3 hours, in embodiments about 2 hours following thecombining the dialdehyde and the non-polymeric cis-hydroxyl compound toform the competing agent. In embodiments, the combination in water isheated to about 60° C. to 100° C. for about 15 minutes to 6 hours toform the competing agent. In embodiments, the combining is carried outin water at a concentration that provides about 40 wt % to 80 wt % ofthe competing agent at the end of the reaction, for example about 50 wt% to 80 wt %, or about 60 wt % to 80 wt %, or about 40 wt % to 70 wt %,or about 40 wt % to 60 wt % of the competing agent. In some embodiments,the pH of the reaction solution is adjusted to about 6.0 to 6.5, inembodiments 6.0 to 6.1. In other embodiments, the pH is not adjusted. Insome embodiments, the pH of the reaction solution decreases as thereaction progresses. In some embodiments, the pH of the reaction productwhen no pH adjustment is carried out is about 4 to 5.

In embodiments, the method comprises combining the competing agentsolution, the crosslinker composition, a water source, and acrosslinkable polymer to form an injectable solution. The order ofaddition or additions may be varied with the proviso that the competingagent is present when the crosslinker composition or any compositioncomprising a crosslinker for the crosslinkable polymer is combined withthe crosslinkable polymer.

In embodiments, the method comprises combining the competing agentsolution and the crosslinker composition to form thedelayed-crosslinking composition, and combining the delayed-crosslinkingcomposition with the water source and the dry polymer. In otherembodiments, the crosslinkable polymer is dissolved in and/or slurriedin a solvent to form a polymer solution, the competing agent solutionand the crosslinker composition are combined to form adelayed-crosslinking composition, and the delayed-crosslinkingcomposition and the polymer solution are combined with a water source toform an injectable solution. In some embodiments, the crosslinkablepolymer is dissolved and/or slurried in a solvent comprising, consistingof, or consisting essentially of the water source to form a polymersolution. In embodiments, the water source comprises, consists of, orconsists essentially of produced water, tap water, groundwater, surfacewater, seawater, wastewater, or any combinations thereof. In some suchembodiments, the water excludes or substantially excludes one or morereactive species.

Advantageously, the combining the delayed-crosslinking composition withthe water source and the crosslinkable polymer to form an injectablesolution is effected at a location proximal to a supply or reservoir ofthe water source (herein, a “location proximal to the water source”). Inembodiments the water source is produced water, and the locationproximal to the water source is in the vicinity of an oil recovery site,an oil well, and/or a structure in communication with a subterraneanreservoir. In some such embodiments, the crosslinker composition and thecompeting agent are conveyed from their respective manufacturinglocations (which in some embodiments are the same, in other embodimentsare different from each other) to the location proximal to the watersource, and the method comprises combining the competing agent and thecrosslinker composition to form the delayed-crosslinking composition inthe location proximal to the water source and combining thedelayed-crosslinking composition with the water source and acrosslinkable polymer to form an injectable solution. In other suchembodiments, the method comprises combining the competing agent and thecrosslinker composition to form the delayed-crosslinking composition,transporting the delayed-crosslinking composition to the locationproximal to the water source, and combining the delayed-crosslinkingcomposition with water source and a crosslinkable polymer to form aninjectable solution.

In embodiments, the method of the third embodiments further comprisesinjecting the injectable solution into a subterranean reservoir; andrecovering a hydrocarbon from the reservoir. In embodiments, thehydrocarbon comprises, consists of, or consists essentially of crudeoil. In some embodiments, the combining the delayed-crosslinkingcomposition with the water source and the crosslinkable polymer to forman injectable solution is effected batch-wise—that is the combining iscompleted before the injecting the injectable solution. In otherembodiments, the combining the delayed-crosslinking composition withwater source and a crosslinkable polymer to form an injectable solutionis carried out continuously. In such embodiments, the crosslinkablepolymer is first dissolved and/or dispersed in a solvent comprising,consisting of, or consisting essentially of water to form a polymersolution; and the polymer solution, a water source, and thedelayed-crosslinking composition are combined in a continuous flowbasis, either by combining a flow of the water source and thedelayed-crosslinking composition to form a first mixture and thencombining a flow of the polymer solution with a flow of the firstmixture, or by combining a stream of the water source with a stream ofthe polymer solution to form a second mixture and then combining a flowof the delayed-crosslinking composition with a flow of the secondmixture, or by combining a flow of the delayed-crosslinking composition,a flow of the polymer solution, and a flow of the water source. In someembodiments, the solvent comprises, consists of, or consists essentiallyof produced water. In some embodiments, the water source comprises,consists of, or consists essentially of produced water.

In embodiments, the method comprises injecting the injectable solutionimmediately after the combining of the delayed-crosslinking compositionwith the water source and the crosslinkable polymer. In embodiments, themethod comprises injecting the injectable solution substantiallyimmediately, in embodiments between 5 seconds and 30 seconds, inembodiments 5 seconds and 60 seconds, or in embodiments 5 seconds and120 seconds after the combining the delayed-crosslinking compositionwith the crosslinkable polymer.

In embodiments, the method comprises combining the competing agentsolution, the polymer, and the water source to form a reactive premix,applying the crosslinker composition to the reactive premix to form aninjectable solution, injecting the injectable solution into asubterranean reservoir, and recovering a hydrocarbon from the reservoir.In embodiments, the hydrocarbon is crude oil. In embodiments, theapplying the crosslinker composition to the reactive premix to form aninjectable solution is effected substantially immediately before theinjecting the injectable solution into a subterranean reservoir, inembodiments, between 5 seconds and 30 seconds, in embodiments 5 secondsand 60 seconds, in embodiments 5 seconds and 120 seconds before theinjecting.

In third embodiments, the molar ratio of the competing agent tozirconium complex is from 1:2 to 1:7, in embodiments from 1:2 to 1:5, inembodiments from 1:3 to 2:9, in embodiments about 1:4, in embodiments1:3.9.

In embodiments, 30 seconds to 300 seconds after the combining of thedelayed-crosslinking composition with the water source and thecrosslinkable polymer, the injectable solution reaches a peak viscosityas measured at 100 s⁻¹ of about 100 cP to about 10,000 cP at atemperature of between 20° C. and 80° C. In embodiments, 30 seconds to300 seconds after the combining of the delayed-crosslinking compositionwith the water source and the crosslinkable polymer, the injectablesolution reaches a peak viscosity as measured as at 100 s⁻¹ of about1,000 cP to about 1,800 cP at a temperature of between 20° C. and 80°C., in embodiments 60 seconds to 240 seconds, in embodiments 60 secondsto 180 seconds, in embodiments 60 seconds to 150 seconds.

Crosslinking is initiated by combining the crosslinker composition withthe crosslinkable polymer. As noted supra, the competing agent of theinvention is advantageously present when the crosslinker composition iscombined with the polymer so that the competing agent provides a delayto the crosslinking reaction that delays the increase of viscosity ofthe injectable solution, the delay allowing time for the injectablesolution to be injected into a subterranean formation and sufficientlypenetrate the formation before a large viscosity increase. Surprisingly,the competing agent provides a suitable delay in crosslinking followedby rheological stability at temperatures above about 150° C. (above 300°F.). Employing the methods of the present invention, the delay period isevidenced by a delay in the onset of viscosity increase of theinjectable solution of about 30 seconds to 8 minutes, or about 30seconds to 7 minutes, or about 30 seconds to 6 minutes, or about 45seconds to 6 minutes, or about 1 minute to 6 minutes, or about 1 minute30 seconds to 6 minutes, or about 2 minutes to 6 minutes, or about 2minutes 30 seconds to 6 minutes, or about 3 minutes to 6 minutes, orabout 30 seconds to 5 minutes 30 seconds, or about 30 seconds to 5minutes, or about 30 seconds to 4 minutes 30 seconds, or about 30seconds to 4 minutes, or about 30 seconds to 3 minutes 30 seconds, orabout 30 seconds to 3 minutes, or about 1 minute to 4 minutes, or about2 minutes to 4 minutes. Such a delay is sufficient to enable pumping theinjectable solution through the injection equipment and associated pipesetc. at a low viscosity.

Viscosity of the injectable solution then increases downhole and/orwithin the subterranean reservoir, where permeability differencesbetween different areas of the reservoir are advantageously addressedand wherein proppant is advantageously transported into the fracturesformed in the rock by the injectable solution during application ofhydraulic pressure thereto. Further, conditions within the subterraneanreservoir often include temperatures over about 20° C., for exampleabout 30° C. to 200° C. and often about 50° C. to 180° C., for exampleabout 60° C. to 180° C. or about 65° C. to 170° C. For this reason,viscosity measurements in the laboratory are determined over a range oftemperatures from about 20° C. to 200° C. in order to more accuratelypredict initial and peak viscosities of the injectable solutions of theinvention in the field.

In embodiments, the peak viscosity of the injectable solution peaks atfrom about 1000 cP to about 1800 cP when measured at 100 s⁻¹ whensubject to a temperature increasing from about 20° C. to about 120° C.over a period of about five minutes, as determined by one of skill uponforming an injectable solution. It is an advantage of the methods andcompositions of the invention that use the injectable solutions providessubstantially the same peak viscosity as would be achieved with the sameinjectable solution exclusive of the competing agent and injected intothe same reservoir, but also to provide a suitable delay.

Fourth Embodiments

In fourth embodiments, there is provided a method of recovering ahydrocarbon from a subterranean reservoir, the method comprisinginjecting the injectable solution of any of the first embodiments into asubterranean reservoir, and recovering a hydrocarbon from the reservoir.In embodiments, the hydrocarbon is crude oil.

In embodiments, the temperature of the subterranean reservoir is from15° C. to 200° C., in embodiments 30° C. to 180° C., in embodiments 40°C. to 180° C.

Further Discussion of the Embodiments

The competing agent of the first, second, third, or fourth embodimentsis the reaction product of a dialdehyde and a non-polymeric cis-hydroxylcompound. Applicants have found that the competing agent advantageouslyprovides a delay in the crosslinking of crosslinkable polymers such aspolysaccharides by crosslinkers such as dissolved reactive boron speciesin produced water and/or zirconium complexes such as zirconium (IV)triethanolamine complexes. The competing agent can be used in injectablesolutions for high temperature applications such as injectable solutionsthat are subject to temperatures of up to 200° C., for exampleinjectable solutions that penetrate hot subterranean formations having atemperature of up to 200° C. The competing agent can also be used todelay crosslinking in injectable solutions made from produced watersincluding high-solids produced waters containing various reactivespecies capable of crosslinking the crosslinkable polymers, reactivespecies such as borates and multivalent cations.

In the first, second, third, and fourth embodiments, the competing agentis formed by combining a dialdehyde (such as glyoxal) and anon-polymeric cis-hydroxyl compound (such as sorbitol) to form a mixtureexcluding or substantially excluding a crosslinker. For example, ifglyoxal or another dialdehyde is added to a crosslinker such as azirconium (IV) triethanolamine complex or a boron crosslinker beforereacting the glyoxal with the sorbitol, the dialdehyde such as glyoxalbinds to the crosslinker and is less available for reaction with asubsequently added cis-hydroxyl compound such as sorbitol.

The competing agent of the first, second, third, or fourth embodimentsis the reaction product of a dialdehyde and a non-polymeric cis-hydroxylcompound. In embodiments, the dialdehyde is a water soluble dialdehyde.In embodiments, the dialdehyde has 2 to 4 carbons total and 0 to 2carbons between aldehyde moieties. In embodiments, the dialdehyde isselected from glyoxal, maleic dialdehyde, fumaric dialdehyde, glutaricdialdehyde, and the reaction product of glucose with NaIO₄. Inembodiments, the dialdehyde is glyoxal. In embodiments, the competingagent is the reaction product of the dialdehyde and the non-polymericcis-hydroxyl compound in a 3:1 to 1:3 molar ratio, in embodiments 2:1 to1:2 molar ratio, in embodiments about a 1:1 molar ratio. In embodiments,the dialdehyde and the cis-hydroxyl compound are combined in water inabout a 3:1 to 1:3 molar ratio, or in about a 2:1 to 1:2 molar ratio, orin about a 1:1 molar ratio to form a combination in water. In some suchembodiments, the combination in water is left for 1-3 hours, inembodiments about 2 hours to form a competing agent solution. Inembodiments, the combination in water is heated to about 60° C. to 100°C. for about 15 minutes to 6 hours to form a competing agent solution.In embodiments, the combining is carried out in water at a concentrationthat provides about 40 wt % to 80 wt % of the competing agent at the endof the reaction, for example about 50 wt % to 80 wt %, or about 60 wt %to 80 wt %, or about 40 wt % to 70 wt %, or about 40 wt % to 60 wt % ofthe competing agent. In some embodiments, the pH of the reactionsolution is adjusted to about 6.0 to 6.5, in embodiments 6.0-6.1. Inother embodiments, the pH is not adjusted. In some embodiments, the pHof the reaction solution decreases as the reaction progresses. In someembodiments, the pH of the reaction product when no pH adjustment iscarried out is about 4 to 5.

In some embodiments, the competing agent solution is added along with acrosslinkable polymer to at least one water source to form a polymersolution comprising a competing agent. In other embodiments, thecompeting agent solution is added to a crosslinker composition to form adelayed-crosslinking composition. The delayed-crosslinking compositionis combined with the polymer and the at least one water source or anaqueous solution of the polymer and the at least one water source toform an injectable solution. In still other embodiments, the competingagent solution is added directly to the aqueous solution of the polymer.The competing agent is added to the injectable solution at about 0.01 wt% to 1 wt %, or about 0.05 wt % to 1 wt %, or about 0.1 wt % to 1 wt %,or about 0.01 wt % to 0.9 wt %, or about 0.01 wt % to 0.8 wt %, or about0.01 wt % to 0.7 wt %, or about 0.01 wt % to 0.6 wt %, or about 0.01 wt% to 0.5 wt %, or about 0.01 wt % to 0.4 wt %, or about 0.01 wt % to 0.3wt %, or about 0.01 wt % to 0.2 wt %, or about 0.05 wt % to 0.5 wt %, orabout 0.1 wt % to 0.5 wt % in the injectable solutions of the invention.Alternatively, the competing agent is added to the injectable solutionin a concentration of about 1×10⁻⁴ M (molar) to about 1×10⁻⁶ M.

One of skill will appreciate that the amount of competing agent added tothe polymer solution is suitably adjusted according to the amount ofdissolved reactive species (if any) in the produced water targeted toform the injectable solutions of the invention and the amount of the oneor more crosslinkers in the injectable solution.

In embodiments, the non-polymeric cis-hydroxyl compound of the first,second, third, or fourth embodiments is a water-soluble non-polymericcis-hydroxyl compound. In embodiments, the non-polymeric cis-hydroxylcompound is a sugar alcohol. In embodiments, the non-polymericcis-hydroxyl compound is selected from the group consisting of sugaralcohols having 3 to 7 carbons and at least one cis-hydroxyl moiety orcis-hydroxyl oligomers having a molecular weight of less than 10,000g/mol. In embodiments, the non-polymeric cis-hydroxyl compoundcomprises, consists of, or consists essentially of a vinyl alcoholhead-to-tail oligomer having a weight average molecular weight of about500 g/mol to 5,000 g/mol. In embodiments, the sugar alcohol having 3 to7 carbon atoms is selected from erythritol, threitol, pentaerythritol,arabitol, xylitol, ribitol, mannitol, sorbitol, galactitol, fucitol,iditol, inositol, volemitol, glycerol, or any combination thereof. Inembodiments, the non-polymeric cis-hydroxyl compound is sorbitol. Inembodiments, the non-polymeric cis-hydroxyl compound comprises, consistsof, or consists essentially of glycerol.

The crosslinkable polymer of the first, second, third, or fourthembodiments has a weight average molecular weight of greater than about10,000 g/mol and up to about 10,000,000 g/mol.

In some embodiments, the crosslinkable polymer of the first, second,third, or fourth embodiments is a polysaccharide having at least 50 mole% repeat units comprising one or more cis-hydroxyl moieties. Acis-hydroxyl moiety is a pair of hydroxyl groups situated in aconfiguration such as a 1,2 configuration, wherein the hydroxyls areconfigured to allow the coordination thereof with the central atom of acoordination complex or crosslinker such as a borate oxyanion. Suchconfigurations include cis-1,2-hydroxy groups on rigid ring structuressuch as sugars and on unsaturated C═C bonds as well as compounds havingfreely rotating C—C bonds wherein both carbons bear hydroxyl moietiesand wherein rotation of the C—C bond can produce hydroxyls in asubstantially eclipsed configuration when viewed as a Newman projection.Collectively, such compounds are denoted cis-hydroxyl compounds.

In other embodiments, the crosslinkable polymer of the first, second,third, or fourth embodiments is a polysaccharide having less than 50mole % repeat units comprising one or more cis-hydroxyl moieties.

In embodiments, the crosslinkable polymer has a weight average molecularweight of about 10,000 g/mol to 10,000,000 g/mol, or about 20,000 g/molto 10,000,000 g/mol, or about 30,000 g/mol to 10,000,000 g/mol, or about40,000 g/mol to 10,000,000 g/mol, or about 50,000 g/mol to 10,000,000g/mol, or about 60,000 g/mol to 10,000,000 g/mol, or about 70,000 g/molto 10,000,000 g/mol, or about 80,000 g/mol to 10,000,000 g/mol, or about90,000 g/mol to 10,000,000 g/mol, or about 100,000 g/mol to 10,000,000g/mol, or about 200,000 g/mol to 10,000,000 g/mol, or about 300,000g/mol to 10,000,000 g/mol, or about 500,000 g/mol to 10,000,000 g/mol,or about 1,000,000 g/mol to 10,000,000 g/mol, or about 20,000 g/mol to9,000,000 g/mol, or about 20,000 g/mol to 8,000,000 g/mol, or about20,000 g/mol to 7,000,000 g/mol, or about 20,000 g/mol to 6,000,000g/mol, or about 20,000 g/mol to 5,000,000 g/mol, or about 20,000 g/molto 4,000,000 g/mol, or about 20,000 g/mol to 3,000,000 g/mol, or about20,000 g/mol to 2,000,000 g/mol. In embodiments, the crosslinkablepolymer comprises at least 10 mole % repeat units comprising one or morecis-hydroxyl moieties, for example 10 mole % to 100 mole %, or about 20mole % to 100 mole %, or about 30 mole % to 100 mole %, or about 40 mole% to 100 mole %, or about 50 mole % to 100 mole %, or about 60 mole % to100 mole %, or about 70 mole % to 100 mole %, or about 80 mole % to 100mole %, or about 90 mole % to 100 mole %, or substantially 100 mole %repeat units comprising one or more cis-hydroxyl moieties.

In embodiments, the crosslinkable polymer of the first, second, third,or fourth embodiments comprises, consists of, or consists essentially ofa polysaccharide. Herein, the term “polysaccharide” includes not onlyunfunctionalized polysaccharides such as guar gum, but alsofunctionalized polysaccharides or derivatives of polysaccharides such ascarboxymethylguar, hydroxyethylguar, carboxymethyl hydroxyethylguar,hydroxypropylguar (HPG), and carboxymethyl hydroxypropyl guar. Inembodiments, the carboxylic groups of carboxymethyl hydroxypropyl guarparticipate in a crosslinking reaction with the one or morecrosslinkers.

In embodiments, the crosslinkable polymer of any of the first, second,third, or fourth embodiments is selected from guar gum,carboxymethylguar, hydroxyethylguar, carboxymethyl hydroxyethylguar,hydroxypropylguar (HPG), and carboxymethyl hydroxypropyl guar. Inembodiments, the crosslinkable polymer of the first, second, third, orfourth embodiments comprises, consists of, or consists essentially of aguar gum. In embodiments, the crosslinkable polymer of the first,second, third, or fourth embodiments comprises, consists of, or consistsessentially of carboxymethyl hydroxypropyl guar. In some suchembodiments, the crosslinkable polymer is the sodium salt ofcarboxymethyl hydroxypropyl guar.

In embodiments, the crosslinkable polymer comprises, consists of, orconsists essentially of one or more galactomannan polymers having aweight average molecular weight of about 50,000 g/mol to 8,000,000g/mol, or about 100,000 g/mol to 5,000,000 g/mol, or about 1,000,000g/mol to 3,000,000 g/mol. Galactomannan polymer, as employed herein,refers to those naturally occurring polysaccharides derived from variousendosperms of seeds. They are primarily composed of D-mannose andD-galactose units. Examples of some plants producing seeds containinggalactomannan gums include tara, huizache, locust bean, palo verde,flame tree, guar bean plant, honey locust, lucerne, Kentucky coffeetree,Japanese pagoda tree, indigo, henna, rattlebox, clover, fenugreek, andsoybean. In some embodiments, the polysaccharide is provided in aconvenient dry, particulate form generally smaller than what is retainedon a No. 20 mesh sieve (U.S. Standard Sieve Series) but larger than thatwhich passes through a No. 200 mesh sieve.

In embodiments, the crosslinkable polymer comprises, consists of, orconsists essentially of a guar gum and/or one or more guar derivativesselected from guar gum, locust bean gum, karaya gum, carboxymethylguar,hydroxyethylguar, carboxymethyl hydroxyethyl guar, hydroxypropylguar(HPG), carboxymethyl hydroxypropyl guar, or any combination thereof.Guar is a branched copolymer composed of a mannose backbone withgalactose branches; the ratio of mannose to galactose in guar isdependent on and characteristic of the endosperm from which it isderived. The mole ratio of mannose to galactose in guar can range, forexample, from 1:1 to more than 3:1. The crosslinkable polymer cancomprise cis-1,2 hydroxyl groups and/or carboxymethyl and/orhydroxyalkyl groups that participate in reaction with the crosslinker.

The polysaccharide is generally provided in solid, powder form, or in ahydrocarbon such as diesel or kerosene. When added to a neutral oracidic aqueous solution such as a neutral or acidic water source, thepolysaccharide hydrates to form an aqueous solution of the polymer.Hydration of the polysaccharides, e.g., guar or HPG, will only takeplace under neutral or acidic conditions, that is, at a pH of about 7 orless. Prior to forming the injectable solution, the aqueous solution ofthe polymer has a viscosity in some embodiments of about 100 cP or lesswhen measured at a shear rate of about 100 s⁻¹, for example about 5 cPto 100 cP, or about 10 cP to 100 cP, or about 15 cP to 100 cP, or about20 cP to 100 cP, or about 25 cP to 100 cP, or about 30 cP to 100 cP, orabout 35 cP to 100 cP, or about 40 cP to 100 cP, or about 45 cP to 100cP, or about 50 cP to 100 cP, or about 5 cP to 95 cP, or about 5 cP to90 cP, or about 5 cP to 85 cP, or about 5 cP to 80 cP, or about 5 cP to75 cP, or about 5 cP to 70 cP, or about 5 cP to 65 cP, or about 5 cP to60 cP, or about 5 cP to 55 cP, or about 5 cP to 50 cP, or about 10 cP to90 cP, or about 20 cP to 80 cP, or about 30 cP to 80 cP, or about 40 cPto 80 cP, or about 50 cP to 80 cP. One of skill will understand that theviscosity of the polymer solution is selected to meet the requirementsof the particular reservoir and equipment employed to apply to thereservoir such polymer solutions and/or injectable solutions formed fromthem.

The hydration is carried out using standard admixing procedures familiarto one of skill. After the combining, in some embodiments a suitableperiod of time is provided for hydration and full dissolution of thecrosslinkable polymer. A suitable period of hydration is dependent ontemperature, pH, ionic content and total dissolved solids of theproduced water and the polymer solution, in addition to concentrationand molecular weight of the crosslinkable polymer in the polymersolution. The hydration period is sufficient to provide maximumviscosity of the combination, an indication of maximum hydrodynamicvolume of the polymer. In some embodiments, hydration of thecrosslinkable polymer is achieved in about 30 seconds to about 10minutes, or about 1 minute to 10 minutes, or about 1 minute to 5minutes, or about 1 minute to 3 minutes. In some embodiments, agitationof the polymer solution is continued throughout the hydration period.

In embodiments, the amount of crosslinkable polymer in the polymersolution is about 10 ppt (parts per thousand) to 200 ppt, or about 10ppt to 180 ppt, or about 10 ppt to 160 ppt, or about 10 ppt to 140 ppt,or about 10 ppt to 120 ppt, or about 10 ppt to 100 ppt, or about 10 pptto 80 ppt, or about 10 ppt to 60 ppt, or about 10 ppt to 50 ppt, orabout 10 ppt to 40 ppt, or about 10 ppt to 30 ppt, or about 10 ppt to 20ppt, or about 12 ppt to 100 ppt, or about 14 ppt to 100 ppt, or about 16ppt to 100 ppt, or about 18 ppt to 100 ppt, or about 20 ppt to 100 ppt,or about 15 ppt to 50 ppt, or about 15 ppt to 30 ppt.

In embodiments, the injectable solution of the first, second, third, orfourth embodiments comprises one or more further additives selected froma proppant, biocide, demulsifier, clay stabilizer, surfactant, gelstabilizer, pH adjusting agent, scale inhibitor, or any combinationthereof. Examples of suitable biocides include Nalco Champion productsEC6297A, EC6116A, EC6111A, or EC9555A (available from Nalco Champion ofHouston, Tex.), or a combination of two or more thereof. Biocides areadded to the polymer solution or the injectable solution to provide atotal concentration of about 200 ppm to 2000 ppm. Examples of suitablesurfactants include ST/IFT management agents such as Nalco Championproduct FFS100E, wettability agents such as Nalco Champion products6191X or FFS100E, or non-emulsifying agents such as Nalco Championproducts ASP301 or FNE200, and combinations thereof. Surfactants areadded to the polymer solution or the injectable solution to provide atotal concentration of about 250 ppm to 2000 ppm. Examples of suitablescale inhibitors include phosphonates, phosphate esters polymericorganic acids, or a combination thereof. Scale inhibitors are added tothe polymer solution or the injectable solution to provide a totalresidual concentration of above 10 ppm in the produced water flowingback from the reservoir for about 6 to 18 months. Examples of suitableclay stabilizers include potassium chloride, tetramethyl ammoniumchloride, choline chloride, Nalco Champion products ASP425, Clay Safe SAor Product 239, or combinations thereof. Clay stabilizers are added tothe polymer solution or the injectable solution to provide a totalconcentration of about 100 ppm to 2 wt %.

Useful pH control agents include bases. Suitable bases for use in themethods of the invention are not particularly limited and include anychemical species or molecular entity that is soluble in water and has anavailable pair of electrons capable of forming a covalent bond with aproton (Brønsted base) or with the vacant orbital of some other species(Lewis base). In embodiments the base is selected from an alkali metalhydroxide, an alkali metal carbonate, or a mixture thereof. Otherpossible pH control agents are Ca(OH)₂, Mg(OH)₂, Bi(OH)₃, Co(OH)₂,Pb(OH)₂, Ni(OH)₂, Ba(OH)₂ and Sr(OH)₂. At temperatures above about 175°F. (79° C.), potassium fluoride is used to prevent the precipitation ofMgO when Mg(OH)₂ is used as a base.

In some embodiments, a buffering agent is employed to buffer theinjectable solution, such that moderate amounts of either a strong baseor acid added to the system—such as inadvertent additions for example—donot cause any large change in pH value of the injectable solution. Thebuffering agent may be a combination of a weak acid and a salt of theweak acid; an acid salt with a normal salt; or two acid salts. Examplesof suitable buffering agents which may be employed to provide aninjectable solution having the desired pH value are NaH₂PO₄—Na₂HPO₄;sodium carbonate-sodium bicarbonate; and sodium bicarbonate, or otherlike agents. By employing a buffering agent instead of a simple base, aninjectable solution is provided which is more stable to a variance of pHvalues found in local water supplies, to the influence of acidicmaterials located in formations, and the like.

In embodiments, the injectable solutions of the first, second, third, orfourth embodiments comprises one or more proppants. A proppant employedin hydraulic fracturing is a solid particulate material, typically sand,treated sand, or a man-made ceramic material. The proppant is of a size,shape, and hardness suitable for keeping an induced hydraulic fractureopen during or following a hydraulic fracturing process. The proppant isadded to the injectable solution in an amount that differs depending onthe type of fracturing process employed and the point in the processwhere the proppant is injected. More viscous injectable solutions arecapable of delivering higher amounts of proppant. The amount of proppantis not particularly limited and is variable depending on the injectionsolution composition as well as the intended use. In embodiments, theinjectable solution further comprises one or more additional componentsselected from a gel breaker, a demulsifier, a clay stabilizer, abiocide, a scale inhibitor, one or more surfactants, a pH adjuster, or amixture of two or more thereof.

In embodiments, the injectable solutions of the first, second, third, orfourth embodiments comprise a gel breaker. The gel breaker is optionallyemployed to predictably degrade the set gel, i.e., the crosslinkedpolysaccharide, after a predetermined period of time. The gel breakersare generally either enzymes or oxidizing agents. The specific gelbreaker employed will depend on the temperature to which the set gel issubjected. Suitable gel breakers include KBrO₃ and similar materials,e.g., KClO₃, KIO₃, peroxides, perborates, persulfates, permanganates(for example, ammonium persulfate, sodium persulfate, and potassiumpersulfate), sodium bromate, and the like, are used to break theboron-mediated crosslink structure. Suitable enzymes include those thatcatalyze the hydrolysis of the glycosidic bonds between the monomerunits of the polysaccharide. The selection of a suitable enzyme for aparticular crosslinkable polymer such as guar or HPG can be determinedfrom references well known to those of skill. The amount of enzymeemployed in any particular gel solution as defined herein will depend onthe amount of crosslinkable polymer present, and also upon thetemperature and pH to which the crosslinked crosslinkable polymer is tobe subjected. It is noted, however, that produced water that startsflowing back from the reservoir once hydraulic pressure is releasedusually has a pH ranging from 6 to 8 which helps break the crosslinkjunctions, thus aiding in injectable solution recovery.

Produced Water

In embodiments, any of the water sources of the first, second, third,and fourth embodiments comprises, consists of, or consists essentiallyof produced water. In some first, second, third, or fourth embodiments,the water sources usefully addressed by the methods of the presentinvention include those sources having at least 10 ppm elemental boron.Concentrations of boron in surface water range widely; however, averageboron concentrations in surface water sources are typically well below0.6 ppm in most regions of the world. In sharp contrast, produced wateroften includes 10 ppm or more of elemental boron. As will beappreciated, water sources containing dissolved reactive species such asproduced waters containing dissolved reactive boron are particularlyimportant for the second embodiments, wherein the crosslinker is solelyprovided by the water source.

In embodiments, the water sources include about 10 ppm to 500 ppmelemental boron present in the water source as dissolved reactive boronspecies, or about 12 ppm to 500 ppm, or about 14 ppm to 500 ppm, orabout 16 ppm to 500 ppm, or about 18 ppm to 500 ppm, or about 20 ppm to500 ppm, or about 25 ppm to 500 ppm, or about 30 ppm to 500 ppm, orabout 35 ppm to 500 ppm, or about 40 ppm to 500 ppm, or about 45 ppm to500 ppm, or about 50 ppm to 500 ppm, or about 55 ppm to 500 ppm, orabout 60 ppm to 500 ppm, or about 65 ppm to 500 ppm, or about 70 ppm to500 ppm, or about 75 ppm to 500 ppm, or about 80 ppm to 500 ppm, orabout 85 ppm to 500 ppm, or about 90 ppm to 500 ppm, or about 95 ppm to500 ppm, or about 100 ppm to 500 ppm, or about 110 ppm to 500 ppm, orabout 120 ppm to 500 ppm, or about 130 ppm to 500 ppm, or about 140 ppmto 500 ppm, or about 150 ppm to 500 ppm, or about 175 ppm to 500 ppm, orabout 200 ppm to 500 ppm, or about 250 ppm to 500 ppm, or about 300 ppmto 500 ppm, or about 350 ppm to 500 ppm, or about 400 ppm to 500 ppm, orabout 450 ppm to 500 ppm, or about 10 ppm to 400 ppm, or about 10 ppm to350 ppm, or about 10 ppm to 300 ppm, or about 10 ppm to 250 ppm, orabout 10 ppm to 200 ppm, or about 10 ppm to 150 ppm, or about 10 ppm to140 ppm, or about 10 ppm to 130 ppm, or about 10 ppm to 120 ppm, orabout 10 ppm to 110 ppm, or about 10 ppm to 100 ppm, or about 20 ppm to300 ppm, or about 20 ppm to 200 ppm, or about 20 ppm to 150 ppm, orabout 20 ppm to 120 ppm elemental boron, present as dissolved reactiveboron species.

Produced water often has a total dissolved solids content at least about1 wt %, and up to about 35 wt %. The dissolved solids include variousions. Table 1 shows representative analyses of some cations as well aschloride anion present in a sample of produced water obtained from thePermian Basin region of the United States, as measured by inductivelycoupled plasma (ICP) analysis or titration in the case of chlorideanion. While these measurements are not a total analysis, one of skillwill appreciate that in addition to dissolved boron species, largeconcentrations of ions, such as sodium, calcium, magnesium, and otherdivalent cations cause solution instability when injectable solutionsare formed using produced water. Instability is evidenced by formationof gel particles, coagulum, polymer coated out on contact surfaces, andthe like. The products of this instability cause plugged equipment inthe field, reduced reservoir permeability, plugged formation, andultimately failure to accomplish mobility control within the reservoir.Further, some ions present in the produced water, such as iron, are alsocapable of ionic or coordination reactions with crosslinkable polymerssuch as guar gum, 2-carboxymethyl hydroxypropyl guar, andcis-hydroxylated compounds. The presence of such ions furthercomplicates attempts to use produced water to provide delayedcrosslinking of the crosslinkable polymer. It is a feature of theinvention that the injectable solutions formed according to theinvention do not suffer from instability in the presence of the variousions, including those that can react with cis-hydroxylated compounds. Itis a feature of the invention that when the competing agent is includedin an injectable solution formed using produced water, observablecrosslinking of crosslinkable polymers, manifested as an increase inviscosity, is delayed for at least 30 seconds and as long as 5 minutes.

TABLE 1 ICP analysis of some elements measured in produced waterobtained from the Permian Basin region. Element Concentration, mg/L Ba1.9 B 39 Ca 1900 Fe 83 Mg 270 K 510 Na 40,000 Sr 440 Cl* 68,000 Si 11*Cl was determined titrimetrically.

In some second embodiments of the invention, the pH of the water sourceemployed in forming the polymer solution is or is adjusted to be about 5to 8, or about 5.1 to 8, or about 5.2 to 8, or about 5.3 to 8, or about5.4 to 8, or about 5.5 to 8, or about 5.6 to 8, or about 5.7 to 8, orabout 5.8 to 8, or about 5.9 to 8, or about 6.0 to 8, or about 6.1 to 8,or about 6.2 to 8, or about 6.3 to 8, or about 6.4 to 8, or about 6.5 to8, or about 5 to 7.9, or about 5 to 7.8, or about 5 to 7.6, or about 5to 7.4, or about 5 to 7.2, or about 5 to 7.0, or about 5 to 6.9, orabout 5 to 6.8, or about 5 to 6.7, or about 5 to 6.6, or about 5 to 6.5,or about 5 to 6.4, or about 5 to 6.3, or about 5 to 6.2, or about 5 to6.1, or about 5 to 6.0, or about 5 to 5.9, or about 5 to 5.8, or about 5to 5.7, or about 5 to 5.6, or about 5 to 5.5, or about 5 to 5.4, orabout 5 to 5.3, or about 5.5 to 7, or about 5.5 to 6.5. In some suchsecond embodiments, the water source employed to form the polymersolution has a pH within the suitable range, and no adjustment of pH iscarried out prior to forming a polymer solution from the water source.In other second embodiments, the pH is lower than 5 or higher than 8 andadjustment is necessary to provide pH in a suitable range for polymersolution formation. In some second embodiments, a water source having apH of less than 5 is acceptable to use in forming the polymer solution,since the low pH prevents substantial crosslinking by the dissolvedreactive boron species. However, in other second embodiments use ofwater source having a pH of less than about 5 is impractical due to theamount of pH adjustment agent required in order to increase the pH to8.5 or greater during formation of the injectable solution, loweredsolubility of the crosslinkable polymer, or both. Thus in the secondembodiments, where pH of the water source is less than about 5, it is aselection of the user to adjust the pH to 5 or greater or simply use thewater source without adjusting the pH prior to forming the polymersolution.

Agents employed to adjust the pH of the water source to about 5 frombelow about 5 are bases. Suitable bases for use in the methods of theinvention are not particularly limited and include any chemical speciesor molecular entity that is soluble in water and has an available pairof electrons capable of forming a covalent bond with a proton (Brønstedbase) or with the vacant orbital of some other species (Lewis base).Commonly employed bases include sodium, potassium, or calcium hydroxide.Agents employed to adjust the pH of the water source to about 6.5 orless starting from a pH above about 6.5 are acids. Suitable acids foruse in the methods of the invention are not particularly limited andinclude any chemical species or molecular entity that is soluble inwater and capable of donating a proton (Brønsted acid) or capable offorming a covalent bond with an electron pair (Lewis acid). Commonlyemployed acids include sulfonic acid, phosphoric acid, hydrochloricacid, organic acids such as citric acid or acetic acid, sulfamic acid,and nitric acid. The amount of acid or base is not limited and are addedin a suitable amount to reach the target pH, as will be understood bythose of skill.

EXAMPLES Example 1: Aqueous Competing Agents

A round-bottom flask was charged with a 40% by weight solution ofglyoxal in water (amounts given in Table 2), and mixing was started. Tothe glyoxal solution in the flask was added a 70% by weight solution ofsorbitol in water (amounts given in Table 2), and the contents of theflask were mixed until homogenous. The pH of the solution in the flaskwas monitored. To the contents of the flask was added aqueous sodiumhydroxide (50% by weight solution in water) to raise the pH of theliquid to between 6.0 and 6.1. The solution was stirred for a furthertwo hours at room temperature.

TABLE 2 Amount Amount Amount of 50% Competing of 40% of 70% sodiumApproximate Agent glyoxal/ sorbitol/ hydroxide/ mole ratio of Solutiongram gram gram glyoxal:sorbitol A 131.99 246.62 0.50 1:1 B 290.20 260.241.00 2:1 C 145.10 520.49 2.18 1:2

Example 2: Crosslinker Solution

A 500 ml round-bottom flask was charged with 117 grams of a 70% byweight solution of zirconium tetra(n-propoxide) in n-propanol, andmixing was started. The temperature of the contents of the flask wascontinuously monitored. To the zirconium tetra(n-propoxide) solution wasadded dropwise triethanolamine to control the exotherm. Thetriethanolamine was added over approximately 35 minutes and the maximumtemperature attained was about 46° C. (115° F.). The contents of theflask were stirred for a further approximately 85 minutes giving a totalreaction time of about 120 minutes. During this 85 minute-period, thecontents were allowed to cool to about 38° C. (100° F.) and weremaintained at this temperature for the remainder of the 85 minute periodby heating. The contents were then cooled to room temperature to yieldthe crosslinker solution.

Example 3: Delayed-Crosslinking Compositions

Each competing agent solution (2 mL) from EXAMPLE 1 was individuallymixed with a portion of the crosslinker solution from EXAMPLE 2 to givean delayed-crosslinking composition, as shown in Table 3:

TABLE 3 Delayed-crosslinking composition solution Competing agentsolution Crosslinker solution D 2 mL of competing agent 35 mL ofcrosslinker solution A solution E 2 mL of competing agent 35 mL ofcrosslinker solution B solution F 2 mL of competing agent 35 mL ofcrosslinker solution C solution

Example 4: Injectable Solutions' Viscosity Measurements

Each of six injectable solutions was made up by mixing water, 45 poundsper thousand gallons of carboxymethyl hydroxypropyl guar, one gallon perthousand gallons of a demulsifier, one gallon per thousand gallons of aclay stabilizer choline chloride), half a gallon per thousand gallons ofa biocide, half a gallon per thousand gallons of a scale inhibitor, halfa gallon per thousand gallons of a nonionic surfactant, eight gallonsper thousand gallons of a gel stabilizer, three gallons per thousandgallons of aqueous sodium hydroxide (20% by weight solution of sodiumhydroxide in water), and either 1.1 or 1.2 gallons per thousand gallonsof delayed-crosslinking compositions D, E, or F (from Example 3), asshown in Table 4:

TABLE 4 Gallons of delayed- Delayed- crosslinking Injectablecrosslinking composition added/ Solution Water Used composition thousandgallons G Tap water, Fresno, TX D 1.1 H Tap water, Fresno, TX D 1.2 ITap water, Fresno, TX D 1.2 J Tap water, Fresno, TX D 1.1 K Tap water,Fresno, TX E 1.1 L Tap water, Fresno, TX F 1.1

Each of the six injectable solutions was heated to 163° C. (325° F.) ata pressure of 400 psi and the viscosity measured at 100 s⁻¹ using aChandler Engineering Model 5550 Rheometer available from ChandlerEngineering, Tulsa, Okla. over a period of approximately two hoursthirty minutes.

Plots of the viscosity of injectable solutions G, H, and I are shown inFIG. 1; and plots of the viscosity of injectable solutions J, K, and Lare shown in FIG. 2.

As exhibited by the plots of FIGS. 1-2, the viscosity of the injectablesolutions advantageously increased after a delay to a maximum (peak) ofbetween 1200 and 1800 cP (at 100 sec⁻¹), then decreased. After theinitial viscosity increase and peak, injectable solutions G, H, I, J, K,and L each maintained a viscosity in excess of 80 cP for at least 120minutes at about 162.5° C. (about 325° F.).

The invention illustratively disclosed herein can be suitably practicedin the absence of any element which is not specifically disclosedherein. Additionally each and every embodiment of the invention, asdescribed herein, is intended to be used either alone or in combinationwith any other embodiment described herein as well as modifications,equivalents, and alternatives thereof. In various embodiments, theinvention suitably comprises, consists essentially of, or consists ofthe elements described herein and claimed according to the claims. Itwill be recognized that various modifications and changes may be madewithout following the example embodiments and applications illustratedand described herein, and without departing from the scope of theclaims.

1-12. (canceled)
 13. The method of claim 16, wherein the method furthercomprises: combining the delayed-crosslinking composition, a watersource, and a crosslinkable polymer to form an injectable solution;injecting the injectable solution into a subterranean reservoir; andrecovering a hydrocarbon from the reservoir.
 14. The method of claim 13,wherein a temperature within the subterranean reservoir is about 40° C.to 180° C.
 15. The method of claim 13, the method further comprisingadding one or more proppants to the injectable solution prior to theinjecting.
 16. A method comprising: combining and reacting in water adialdehyde having 2 to 4 carbon atoms with a non-polymeric cis-hydroxylcompound to form a competing agent solution comprising a competingagent, wherein the competing agent solution does not comprise azirconium complex or a borate; optionally adjusting a pH of thecompeting agent solution to about 6.0 to about 6.5; combining azirconium (IV) compound and an alkanolamine in one or more solvents toform a crosslinker composition comprising a zirconium complex; andcombining the competing agent solution and the crosslinker compositionto form a delayed-crosslinking composition.
 17. The method of claim 16,wherein a molar ratio of the competing agent to the zirconium complex isfrom 1:3 to 2:9.
 18. The method of claim 16, wherein the alkanolamine istriethanolamine and the zirconium (IV) compound is zirconiumtetra(n-propoxide).
 19. The method of claim 16, wherein the dialdehydeis glyoxal.
 20. The method of claim 16, wherein the non-polymericcis-hydroxyl compound is sorbitol.
 21. The method of claim 16, whereinthe dialdehyde and the non-polymeric cis-hydroxyl compound are combinedand reacted in water in about a 1:1 molar ratio of the dialdehyde to thenon-polymeric cis-hydroxyl compound.
 22. The method of claim 16, whereinthe non-polymeric cis-hydroxyl compound is a C3 to C7 sugar alcoholselected from erythritol, threitol, pentaerythritol, arabitol, xylitol,ribitol, mannitol, sorbitol, galactitol, fucitol, iditol, inositol,volemitol, glycerol, and any combination thereof.
 23. The method ofclaim 16, wherein the temperature of the crosslinking composition ismaintained between about 15° C. and about 70° C. during the combiningthe zirconium (IV) compound and the alkanolamine.
 24. The method ofclaim 16, wherein the crosslinker composition is maintained at atemperature of from about 35° C. to about 40° C. for 90 to 150 minutesafter the combining.
 25. The method of claim 13, wherein thecrosslinkable polymer is a polysaccharide.
 26. The method of claim 13,wherein the crosslinkable polymer is carboxymethyl hydroxypropyl guar.27. The method of claim 13, wherein the water source comprises aproduced water, tap water, groundwater, surface water, seawater,wastewater, or any combination thereof.
 28. A method comprising:Combining and reacting in water a dialdehyde having 2 to 4 carbon atomswith a non-polymeric cis-hydroxyl compound to form a competing agentsolution comprising a competing agent, wherein the competing agentsolution does not comprise a zirconium complex or a borate; optionallyadjusting a pH of the competing agent solution to about 6.0 to about6.5; combining the competing agent solution, a water source, and apolysaccharide to form a reactive premix.
 29. The method of claim 28,wherein the water source excludes one or more reactive species.
 30. Themethod of claim 28, the method further comprising: combining a zirconium(IV) compound and an alkanolamine in one or more solvents to form acrosslinker composition comprising a zirconium complex; combining thecrosslinker composition and the reactive premix to form an injectablesolution; injecting the injectable solution into a subterraneanreservoir; and recovering a hydrocarbon from the reservoir.
 31. Themethod of claim 28, wherein the crosslinker composition is maintained ata temperature of about 35° C. to about 40° C. for 90 to 150 minutesafter the combining.
 32. The method of claim 28, wherein the dialdehydeand the non-polymeric cis-hydroxyl compound are combined and reacted inwater in about a 1:1 molar ratio of the dialdehyde to the non-polymericcis-hydroxyl compound.